1. Field of the Invention
The present invention relates to compressor blades, and in particular to the blades forming the rotor stages of a compressor in a turbo-machine.
2. Summary of the Prior Art
Research into improving compressor performance in a turbo-machine particularly compressors of the axial type, has made it necessary, in order to increase the efficiency of a compression stage constituted by movable blades, to improve the sealing at the tips of the movable blades and to ensure adjustment during operation, taking into account the various expansion factors of mechanical and thermal origin and the deformations derived from the various stresses exerted on the movable rotor parts or on the fixed parts of the associated stator. Thus, wearable sealing members, formed by linings termed "abradable", are placed on the inner surfaces of the casing facing the tips of the movable blades and, in some turbo-machine applications, the tips of the movable blades are provided with shaped elements in the form of teeth, generally called lips, which are able to cooperate with the abradable members to ensure sealing.
Moreover, depending on the operational conditions of the rotor, certain phenomena of vibrational instability of the rotor blades have been observed. In particular, fluttering vibrations may be generated by the aerodynamic flow conditions at the boundary conditions of the blade tip. In some applications, none of the solutions proposed so far is entirely satisfactory. French Patent No. 2 465 067 proposes damping the vibrations of the aerofoil portion of a blade by making a slit in the body of the aerofoil portion, trailing edge side, extending from the free tip towards the root of the blade. The aim of the invention is directed rather towards avoiding the development of vibrations by modifying the aerodynamic conditions at the tip of a blade.